Predictive simulations of damage propagation in laminated composite materials

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When a laminated composite structure is submitted to a low energy impact, damage may appear inside the structure, especially between the plies. The main issue is that, depending on the energy of the impact, this damage is sometimes not visible (Figure 3). Such damages can actually also appear during the handling of the composite part, or as a result of the manufacturing process. This implies that, in order to avoid overdesigns and not neglect the real behavior of composite materials, composite structures must be sized with a damage tolerant approach, allowing the presence of damage or
assuming that damage may be present in the structure even when not visible, in order to determine safe and tight material allowable for the upper stages of the pyramid.
There are of course several ways to address damage with numerical methods. In this paper, the formulation doesn’t rely on a multi-scale approach but is based on the continuum damage mechanics and meso-models of the homogenized plies and of the interface are used, which represent the lowest scale in the modelling (Figure 4). However, the physics represented by these meso-models come from a detailed observation of micro, meso and macroscopic behaviors of the composite material. The approach can be used to study large scale components, well beyond the coupon level.



Delamination is one of the most critical causes of failure in a laminated composite structure. It results in the separation of two adjacent plies, leading to the propagation of an inter-laminar crack. In the finite element method, the cohesive elements approach is often used to model such cracks (Figure 4), and it is the case in this work. Interface elements are then defined between the finite elements representing the plies. A specific material law with a softening behavior is then assigned to this interface. This allows modeling imperfect interfaces, which are interfaces where delamination can appear in case of excessive loading.